Telephone surveys are a form of quantitative market research used to determine and predict attitudes, opinions and behaviors of a particular group based on scientific sampling. The results from telephone surveys are traditionally designed to be representative of the population.
In order to ensure that your results are representative, it is imperative to survey the right people and make sure that the sample size is sufficiently large. Those new to market research are always amazed that you typically only need to survey 384 respondents (most round to 400) to have the results of your survey be representative of a population of a million or more. The actual sample size chosen is also influenced by the level of detail required in the analysis (i.e., number of market segments to be analyzed).
Telephone surveys are administered by trained interviewers skilled at probing and clarifying comments shared by respondents. These interviewers ensure that all the questions are answered, unlike a mail survey in which respondents can choose to skip questions. Your research consultant will have access to these types of interviewers.
It is important to develop a questionnaire that removes the possibility of bias and is organized to maximize the quality of responses. Each word used in the questionnaire must be carefully chosen since subtle nuances can a have huge influence on the results obtained.